Could also be a delayed carb flu. From what I've read here, sometimes carb flu kicks in right about three weeks.
If it IS carb flu, don't worry, it will be gone in two weeks and you'll have a LOT of energy for P90x2. Hang in there and DON'T increase the carbs yet. If you don't feel more energy in 10 days or so, then yes you probably need a few more carbs.
5'0" female, 44 years old. Started Primal October 31, 2011, at a skinny fat 111.5 lbs. Low weight: 99.5 lb on a fast. Gained to 109 on sugar cheat. Reset with 85P / 90C / 90F. Currently weaning off fat to 85P / 90C / 60F.
MY PRIMAL: I (try to) follow by-the-book primal as advocated by Mark Sisson, except for whey powder and a bit of cream. I advocate a two-month strict adjustment for newbies. But everybody is different and other need to tweak Primal to their own needs.